Known for his preternatural performance agility, lightning-fast impressions and malleable voice, Robin Williams was a versatile actor beloved by several generations.

Fun-loving as he seemed, he also was a deeply disciplined actor ever in search of challenge and complicated roles.

Those fans and the Hollywood community were in mourning Monday after the Oscar-winning actor/comic was found dead in his Northern California home, a possible suicide, according to investigators. He was 63.

Baby boomers first became acquainted with him in 1978 as Mork, TV's lovable clownish alien in rainbow-colored suspenders on the Mork & Mindy sitcom.

Williams started out doing improvisational stand-up comedy in the late '70, and those witty reflexes, honed early, made him singular in his comic brilliance. Yet it was his prodigious intelligence, ferocious intensity and charismatic, maniacal and razor-sharp wit — which sometimes seemed to tread on the edge of sanity — that allowed him to reach into the heart of a character in his varied and impressive dramatic roles.

His breakout role in film, an edgy Vietnam War-era DJ in 1987's Good Morning, Vietnam, confirmed his massive likability and spot-on comic timing.

His appeal was one of the broadest among contemporary Hollywood actors. He could play an earnest English professor in Dead Poets Society and a benevolent nanny in Mrs. Doubtfire with equal aplomb. As the quick-witted genie in Aladdin, he easily stole the 1992 movie and won the hearts of the youngest audience members.

He was one of the rare actors who was able to transcend his comic origins and be taken seriously as a dramatic actor. Indeed, he was widely admired in Hollywood, receiving the ultimate honor from his peers, an Oscar for best supporting actor in 1997's Good Will Hunting.

He excelled at playing energetic teachers, the kind we wish we'd had in school, but he was equally adept at playing characters on the edge of lunacy, such as the homeless philosopher in The Fisher King.

Among his 70 movies, he made some bad choices in material. Patch Adams, Popeye and Hook were clunkers, but Williams was indefatigable, always striving for singularly intriguing performances. He worked with some of the industry's most challenging and artistic directors, including Terry Gilliam, Robert Altman and Woody Allen, while still taking roles in more predictable blockbusters that are actors' bread and butter.

Some of his best performances were his darkest roles. His disturbing portrayal of an obsessed loner in 2002's One Hour Photo was eerie and indelible, and that same year he starred as a villainous crime novelist in the taut thriller Insomnia.

His loony-jolly characters were fan favorites, however, perhaps because they were inspired by similarly offbeat comedians. Among those he admired most: Jonathan Winters, Charlie Chaplin, Jackie Gleason and Bill Cosby.

"You're only given a little spark of madness, you mustn't lose it,'' he once said.

When he hit his late 50s and early 60s, Williams had deftly played presidents, most recently Dwight D. Eisenhower in 2013's The Butler and also Teddy Roosevelt in the Night at the Museum movies.

In the last decade, Williams seemed drawn to even more offbeat and provocative roles. Ironically for a man who could easily make audiences laugh hysterically, his serious, darker characters might have left the most indelible impression of all.

Actor Robin Williams, 63, was found unconscious and not breathing inside his home in Tiburon, Calif., on Monday, Aug. 11, 2014. He was pronounced dead of suspected suicide. We remember Williams as we look back at the beloved actor's illustrious career. Todd Plitt, USA TODAY

In 2013 Williams, here with actress Alice Drummond told USA TODAY that his role as Malcom Saver int he 1990 motion picture "Awakenings" was his favorite. The part is based on neurologist Oliver Sacks. Louis Goldman, Columbia Pictures

Williams, center, won an Academy Award in 1998 for best supporting actor in "Good Will Hunting." Matt Damon, left, and Ben Affleck, right, also won for the movie's screenplay. Robert Hanashiro, USA TODAY

Williams donates blood at the Irwin Memorial Blood Center in San Francisco on Sept. 11, 2001. Thousands of people waited in long lines to donate blood for victims of terrorist attacks in New York and in Washington. Justin Sullivan, AP

An avid cyslist, Williams rides with his friend Lance Armstrong during a training session as part of a rest day before the 15th stage of the 89th Tour de France in Saint-Paul-Trois-Chateaux, France in July 2002. Olivier Morin, AFP/Getty Images

Ben Stiller, left, and Williams in a scene from their 2006 movie "Night at the Museum." The third and final installment in the comedy series, "Night at the Museum: Secret of the Tomb" is due in theaters Dec. 19. Doane Gregory, 20th Century Fox

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The man dubbed the "funniest man alive" by Entertainment Weekly in 1997 battled depression and his familiarity with pain and suffering no doubt informed his roles. Comedy, he said, can be a cathartic way to deal with personal trauma.

Williams seemed less like a Hollywood icon and more like a favorite eccentric uncle who could leave everyone in stitches, then turn around and be supremely serious, perhaps even painfully so.

In every role he took, no matter if it were broadly comic or profoundly menacing, Williams injected his singular persona, perhaps even a little too much of himself than was "safe.'' We didn't just marvel at his performances, we also experienced the seething humanity just visible beneath the role. This is perhaps why his loss is so deeply-felt.